The present invention relates to a utility knife that reduces or eliminates the chances of accidental cuts. More particularly, this invention relates to a utility knife with a safety hood which automatically locks closed after the blade is used to make a single cut in a cardboard box or the like.
Utility knives are well known and have a wide variety of uses. A well-recognized problem with these knives is that the user often accidentally cuts his/herself. This can occur when the user is handling and/or carrying the knife or accidentally cutting himself or herself when using the knife.
In many of the uses of utility knives, such as opening boxes or cutting linoleum, the user is often pulling the knife back towards his/her body, which is the most common way the user gets cut. When the knife reaches the edge of the work surface next to the user""s body, the knife is accidentally pulled across the user""s leg or other hand. The likelihood of such an injury is increased when the user is doing repetitive tasks. Many attempts have been made to make utility knives safer. Some of the patents attempting to address this issue are listed below.
U.S. Pat. No. 2,376,887 to Walters (1944) discloses a utility knife with a safety hood which is biased closed with a spring.
U.S. Pat. No. 2,889,623 to Baker (1957) discloses a wallpaper cutter where the cutting blade is forced down from between two rollers by thumb pressure.
U.S. Pat. No. 3,781,988 to Jones (1975) discloses a utility knife with a hood covering the blade. The hood is held down over the blade with a spring. Pressure on the bottom of the hood will expose the knife blade.
U.S. Pat. No. 3,999,290 to Wood (1976) discloses a utility knife with an automatically retracting blade.
U.S. Pat. No. 4,531,286 to Vito et al. (1985) discloses a utility knife with a hood covering the blade. The blade is uncovered by pressing a release lever built into the body. The release lever is depressed by normal gripping of the body. Pressing the bottom of the hood against a box could also expose the blade.
U.S. Pat. No. 4,868,985 to Rehn (1989) discloses a utility knife with an automatically retracting knife blade.
U.S. Pat. No. 5,241,750 to Chomiak (1993) discloses a utility knife with a hood covering the blade. The hood is held down over the blade with a spring. Pressure on the bottom of the hood will expose the knife blade. A lock lever allows the hood to be locked closed.
U.S. Pat. No. 5,386,632 to Schmidt (1995) discloses a utility knife with a retractable blade.
U.S. Pat. No. 5,404,645 to Janser (1995) discloses a utility knife with a moveable blade that can be placed in one of three different positions to provide three different cutting depths.
U.S. Pat. No. 5,494,670 to Quinn (1996) discloses a utility knife with a moveable blade pushed forward by the user.
U.S. Pat. No. 5,522,135 to Votolato (1996) discloses a utility knife with a hood covering the blade. The hood is held down over the blade with a spring. Pressure on the bottom of the hood will expose the knife blade.
U.S. Pat. No. 5,604,984 to Shepherd et al. (1997) discloses a utility knife with a rotary blade magazine. The blades can be moved in and out of the magazine as needed.
U.S. Pat. No. 5,613,300 to Schmidt (1995) discloses a utility knife with a retractable blade.
U.S. Pat. No. 5,617,635 to Berns (1997) discloses a utility knife with an automatically retracting blade.
U.S. Pat. No. 5,909,930 to Ragland, III et al. discloses a utility knife with a retractable blade.
U.S. Pat. No. 5,940,970 to D""Ambro, Sr. et al. discloses a utility knife with a retractable blade.
U.S. Pat. No. 6,070,326 to Berns discloses a utility knife with a retractable blade guard. The blade guard is a wire cage which extends around the blade and retracts back over it. A knife made by Martor-Argentax, assignee of the Berns patent had the same blade guard which is pushed back over the front edge of the blade, exposing the front point first, then sliding back perpendicular to the cutting surface. The blade guard is locked in position over the blade. The user must depress a release latch on the knife to allow the guard to move. Once the guard had moved, exposing the front edge of the blade, the release latch must be release and then re-depressed to release the cover again. The cover slides back into the body of the knife.
The two most common types of xe2x80x9csafety knivesxe2x80x9d have either a retracting blade or a movable hood covering the blade. The retracting blades can be manual or automatic. The manual retractors do not solve the problem of accidental cuts while using the knife. Some of the auto-retracting blades have a button that must be depressed or pushed forward and held to keep the blade but. This reduces many accidental cuts, but often does not solve the problem of cuts that happen coming off the edge of the cutting surface. The user is not likely to release the button the second they reach the edge, particularly if they are cutting multiple things. In addition, keeping the button depressed can cause stress and cramping in the user""s hand. Another danger of the auto-retracting blades is that the user can accidentally have his/her index finger at the front edge of the knife, against the blade, when it is retracted, cutting the finger.
The prior art utility knives with safety hoods are another attempt to reduce accidental cuts. The prior art hoods are generally biased closed with a spring or similar mechanism. Pressing on the bottom edge of the hood pushes the hood back, revealing the blade. Once the pressure on the bottom edge is released the hood closes again. The problem with these hoods is that as the user is drawing the knife across their leg or other body part accidentally they are putting pressure on the bottom edge of the hood, thereby exposing the blade.
The Martor knife with the wire blade guard is another type of safety knife. The Martor knife is designed to push the front edge of the blade through a surface to start the cutting. See FIG. 1a, ""326 patent. Then the knife is pulled thought the working surface, against the cutting edge. This design does not work well for cutting open boxes as it requires puncturing into the box, risking cutting merchandise.
Another problem that is common with the use of utility knives is accidentally cutting what is under the cutting surface. For example, it is a common problem to have merchandise damaged by being accidentally cut when the shipping box is cut open. It is known in the art to restrict the depth of cut of the knife blade by reducing the amount the blade extends from the body of the knife. In the prior art knives the blade can be moved to extend different lengths beyond the body of the knife, allowing different depths of cut. However, all of the prior art knives move the blade of the knife to adjust the depth of cut. This is often a cumbersome process and it is not always easy to switch between cutting depths.
What is needed is a utility knife wherein the blade cannot be accidentally uncovered and will automatically close and lock a hood once the blade is removed from the cutting surface. Additionally the utility knife should allow the user to choose the depth of cut easily and to change easily between depths of cut.
The present invention solves these problems by having an automatically locking hood to cover the blade. The hood cannot move until a button is depressed to release the lock. The knife can then be used to cut a desired surface. The hood rotates back from the cutting edge when pressure is applied at the bottom edge of the hood by the cutting surface. The hood rotating back and then forward again resets the lock so that as soon as the pressure on the bottom edge is removed the hood closes and is re locked. The hood also controls the depth of cut of the blade. A movable, positive stop on the knife is used to control the amount that the hood can rotate back from the edge of the blade, preventing over cutting.
The primary aspect of the present invention is to provide a utility knife which significantly reduces the chances of the user or others being accidentally cut.
Another aspect of the present invention is to provide a utility knife that will automatically lock shut a cover for the blade once a cut is complete.
Another aspect of the present invention is to provide a utility knife that allows for controlling the depth of cut of the blade without the need to move the blade.
Another aspect of the present invention is to provide a utility knife where the depth of cut can easily be changed.
Another aspect of the present invention is to provide a utility knife that does not require the user to constantly keep a button depressed to use the blade.
Another aspect of the present invention is to provide a utility knife with a pivoting safety hood, wherein a traditional downward attach angle of about 45 degrees or less is used to minimized the blade penetration into a box, and, furthermore, the hood automatically is biased to the safety mode as the blade clears the box.
Other aspects of this invention will appear from the following description and appended claims, reference being made to the accompanying drawings forming a part of this specification wherein like reference characters designate corresponding parts in the several views.
The preferred embodiment of the present invention has a safety hood which is pivotally mounted to the body or cover of the knife at the front end. The body is pivotally mounted to a spine at the back end. The blade is removably mounted on the spine such that the hood covers the blade when the knife is closed. The hood is biased closed and has a latch to hold it closed unless the latch is released. The user depresses a button, which moves the latch, releasing the hood to push up when the user presses the hood against a working surface. The upward rotation of the hood releases the latch, so that when the hood rotates down the latch automatically re-locks the hood closed. The hood cannot be release again with out releasing the button and re-depressing the button.
A second embodiment has a safety hood that has two legs extending back to moveably connect the hood to the body of the knife. The legs act as springs to bias the hood down over the blade of the knife. The hood is locked in place over the blade with a safety catch holding one of the legs in place. The safety catch is released by depressing a button on the top of the knife, pushing the safety catch free of the leg, allowing it to move. The user can then use the knife to cut a desired surface.
As the hood rotates up away from the edge of the blade the safety catch is moved back into position to lock the hood. Once the pressure on the bottom surface of the hood is released the legs act as springs, moving the hood back into position covering the blade. As soon as the hood returns to the closed position the safety catch re-engages, locking the hood closed.
A slide on the body controls the amount the hood can rotate back from the blade, controlling the depth of cut of the blade. The slide can be set for a number of pre-determined cutting depths.